Greesemann

Hello everyone. This is an awesome site. I'm greesemann and here is my problem. I just bought a 2000 odyssey 3.5. All is well except the transmission. Here's what happens. I crank it up cold back out of the driveway and drive down the street everything is fine. When the van warms up it feels like I shifted into neutral. I pull over shut the van off restart it and once again shifting normal for a little wile. The trans shifts fine until warm then It feels like it goes into neutral. Does anyone know what this problem might be ? I sure appreciate any and all help and advice. Thanks Greesemann ok I replaced the transmission with a used one did fine for a day then today started the neutral crap again. This time I have trouble codes po740 and p1738. Anyone have some advice? Thanks for your time greesemann